Ammonium Nitrogen Movement in a Coarse-Textured Soil Amended with Zeolite1

C. T. MacKown and

T. C. Tucker2

Abstract

Abstract

Leaching of NH+4 from coarse-textured soils treated with nitrification inhibitors is affected by the soil cation exchange capacity (CEC), the presence of other ions, and the percolation rate. Natural zeolites have unique chemical and physical properties that could enhance the retention of monovalent cations in coarse-textured soils.

Column experiments to evaluate NH+4 movement in Rositas loamy sand (Typic Torripsamment) amended with erionite (E) or clinoptilolite (K) natural zeolite at rates of 0, 12.5, 25.0 and 50.0 g zeolite kg−1 soil were conducted. Water saturated soil-zeolite mixtures (1.0 kg) received 200 mg NH+4-N and were leached with 3.0 liters (150 cm) of deionized water containing a nitrification inhibitor [2-chloro-6-(trichloromethyl) pyridine]. Total NH+4-N leached ranged from 168.4 mg N for the unamended soil (CEC = 29 cmol(+) kg−1) to 11.6 mg N for the 50.0 g E kg soil (CEC = 102 cmol(+) kg−1). Total effluent NH+4-N at a given amendment rate was less from zeolite E(CEC = 1570 cmol(+) kg−1) than zeolite K (CEC = 1140 cmol(+) kg−1). The distribution of NH+4 recovered in 5-cm increments was dependent on the CEC of the soil-zeolite mixture. As the CEC increased, the depth of maximum accumulation decreased. These results indicate that zeolites effectively enhanced the retention of NH+4 subject to leaching and zeolite application per unit soil volume may be maximized by restricting the depth of incorporation.

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